David Cameron must be “honest and upfront” about the Government’s plans to build two new garden cities in Kent and Buckinghamshire,Nick Clegg has said.

The Deputy Prime Minister says that there is “no point hiding” the facts as he insists that a report into the viability of building large new settlements to alleviate Britain’s housing crisis will be published by the Coalition.

His comments, made in an article for The Telegraph, will be seen as a direct challenge to David Cameron to publish a “prospectus” for future developments, which was drawn up after the Prime Minister gave a speech supporting the idea nearly two years ago.

This newspaper understands, from sources outside the Deputy Prime Minister’s office, that a draft proposal suggests building two new settlements in Yalding, Kent, and Gerrards Cross, in Buckinghamshire.

The new cities – which could be comprised of tens of thousands of new homes – would be built in areas considered to be Conservative heartlands and would lead to an outcry from grassroots activists.

In comments that will alarm his Coalition partners, Mr Clegg also admitted that the country’s green belt “is being eaten away” by the expansion of cities.

The Conservatives have repeatedly denied that the report on garden cities exists. However, Mr Clegg writes that “in 2011, our housing strategy committed us to publishing a prospectus for new garden cities and that is exactly what we’ll do”.

Mr Clegg insists that garden cities will only be built “where there is clear local support and private sector appetite”.

Senior Lib Dems are putting pressure on the Conservatives to publish the report by the end of this year, it is understood.

In his article, the Deputy Prime Minister challenges the Conservatives to support the garden city plans even if they are considered to be “electorally unpopular”.

“Already bloated towns and cities are being forced to expand bit by bit, and the green belt is being eaten away,” Mr Clegg says. “We must stop the piecemeal infill and bring an end to the endless controversy about developments that sprawl out from already established areas.

“Garden cities are a way of protecting the countryside. It is possible to create them without building on the green belt, National Parks or Areas of Outstanding Natural Beauty. And by doing it we could deliver homes people can afford in places they want to live.”

The garden cities report has languished in a Whitehall office since it was written over fears that the creation of new cities could lead to Labour voters moving into safe shire constituencies, diluting traditional Tory support.

Garden cities were developed in the early years of the last century in an attempt to combine the best of town and country living and create healthy homes for working people.

Many Tories as well as the Liberal Democrats see them as a solution to the housing shortage.

New homes equivalent to 18 Olympic villages are expected to be needed in London alone by 2021.

The document, which is fewer than 50 pages long, is understood to recommend building at least two communities, modelled on those created by the original garden city movement at Letchworth and Welwyn in Hertfordshire.

In his article, Mr Clegg described an “arc” around the South East where the new cities would be built.

He did not specify specific locations where the new towns could be built. However, senior Government sources have separately told the Telegraph that Yalding and an area near Gerrards Cross are places that have been singled out for development.

“We must also be honest and upfront about where they will be,” Mr Clegg writes. “There’s no point in hiding from it. There is an arc around the South East of England where demand is past breaking point.

The current situation is bad for the economy and places a massive strain on vital services.

“Where there is more work and more demand, we should bite the bullet and create garden towns and garden cities. If you look at places like Welwyn Garden City and Milton Keynes, these are places where planned communities can thrive.”

According to Lib Dem sources, the document was completed more than a year ago, and has been “sat on” ever since.

The Conservatives, however, have attempted to deny the existence of the garden cities report.

In response to a parliamentary question tabled by Cheryl Gillan, the MP for Chesham and Amersham, a minister said that there are “absolutely no plans to impose new towns on any part of the country”.

Kris Hopkins, the housing minister said that he is not “aware of any report which was supposed to have been published by the government but which has been ‘suppressed’.”

“The Government’s policy is to support communities with their ambitions to deliver large scale local development,” Mr Hopkins added.

Why these two locations? Well Yalding was in the Abercrombie plan after world war 2 but there was no agreement between ministries. However both sites are now in the Green Belt. Is this the best way of chooisng sites for Garden Cities, dusting down studies done over 60 years ago! Don’t Labour and the Cons realise you cant do Garden Cities through national dictat, only through a proper city regional plan. Why not break the logjam and publish the report without pinpointing locations.

The Grasslands Trust team blog about nature conservation and broader environmental issues, always with a focus on our threatened grassland habitats. The views in this blog do not necessarily reflect those of the Trust.